The present invention relates to power driven drills, and more particularly to a drilling machine for drilling holes in plaster casts or models.
Various power-driven drilling machines are already known. Such drills typically include a motor drive which is connected, by means of a chuck assembly, to a drill bit which is suitable to form a hole in a work piece when the drill is turned by the motor and simultaneously advanced into the work piece. While some power-driven drills are hand held, numerous known types are available which provide a drilling surface on which a work piece may be securely positioned. While the known machines are frequently satisfactory for the purposes for which they are intended, the machines of the prior art have frequently lacked one or more features which would make them particularly suitable for drilling holes in plaster casts or models frequently used in the field of dental prosthodontics. The exacting specifications and features which are desirable in connection with such work include precise location of the holes which are drilled in the model as well as precise control over the depth to which the holes are drilled. Also of great importance is the characteristic that the holes be drilled in precise normal directions to the surfaces of the model which abut on the drilling surface or platform of the machine.
Many of the machines have not been adaptable for the drilling of numerous holes in a model with great speed and facility. Also, because of the irregular shapes of plaster casts or models, as well as the softness and brittleness of such models, it has not been feasible or practical to rigidly secure the same to the drilling platform and thereby prevent movement of the model during drilling. It has been observed that a suitable approach to prevent movement of the model during drilling is to have the technician performing the drilling hold the model with both hands while urging the same in pressure relationship against the drilling platform. The holding of the model with both hands has not been possible, however, with most prior art drilling machines since one hand has frequently been required to be used for purposes of actuating the machine or for purposes of effecting drilling operations of the machine. For example, according to a one prior art machine, a lever was provided on one side of the machine which required the operator of the machine to grip the same and move the same during the drilling operation. Clearly, such design prevents the technician from using both hands to securely hold the model on the drilling platform.
With respect to drilling machine models of the prior art which included other actuating means, e.g. foot-actuated means, most of these machines have been relatively complex in construction and costly to manufacture. Also, many of the models which have been actuated by means other than hand actuation have not provided the degree of control desirable for controlling the speed with which the drill bit is advanced in the direction of the work piece.
With respect to all of the above-mentioned known drilling machines, none of these have provided simple and effective locating means for indicating the precise locations where the holes were to be drilled. In most instances, the precise locations were not known until the hole to be drilled was actually initiated.
A drilling machine of the type under discussion utilized in the dental arts has not, in the past, been suitable for dental surveying. This has been a drawback of the known machines.